Rotor of a motor device

Abstract

Rotor of a motor device, which includes: a wave (10); a first core part (20) comprising a first press-fit ring (21) into which the shaft (10) is fitted in a press fit, and a plurality of first cores (23) arranged in the circumferential direction of the first press-fit ring (21) such that they hold magnets (50); a second core part (30) comprising a plurality of second cores (31) arranged in the circumferential direction of the first press-fit ring (21) such that they face the first cores (23); and a third core part (40) which is arranged inside the second cores (31) and is installed in such a way that it holds the first press-fit ring (21), the second nuclei (31) have a greater thickness than the first nuclei (23).

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority to Korean Application No. 10-2017-0147161, filed on November 7, 2017, which is incorporated by reference in its entirety. BACKGROUND OF THE INVENTION

[0002] The present invention relates to a rotor of a motor device, and more particularly to a rotor of a motor device in which a first core part can be prevented from being deformed by a press-fitting force of a shaft and a torque density can be improved.

[0003] Generally, a motor has a rotor mounted inside a stator, and a shaft inserted into the rotor's center of rotation. When power is supplied to the stator, the rotor rotates to generate driving force.

[0004] A spoke motor has a rotor structure in which a core and a magnet are arranged circumferentially around a shaft. Since the shaft, made of magnetic material, is press-fitted into the core, magnetic flux leaks through a connection between the core and the shaft. Since a plurality of magnetic flux leakage paths are formed along the shaft in the spoke motor, magnetic flux leakage and a loss of torque density inevitably increase.

[0005] To reduce magnetic flux leakage, an elongated magnetic bridge is installed between the core and the shaft. However, since the magnetic bridge occupies a large area in the radial direction of the rotor, it is difficult to apply the magnetic bridge to the spoke motor, which uses a ferrite permanent magnet and a motor with a hollow rotor.

[0006] Therefore, there is a need for a device capable of solving such a problem.

[0007] The prior art underlying the present invention is described in Korean Patent Publication KR 10 2012 0 110 275 A published on October 10, 2012, entitled "Spoke-type permanent magnet motor." JP 2013-198 304 A discloses a rotor of a motor device comprising a shaft, a first core part including a first press-fit ring into which the shaft is press-fitted, and a plurality of first cores; a second core part including a plurality of second cores arranged in the circumferential direction of the first press-fit ring; and a third core part installed to hold the first press-fit ring. WO 2014 / 169 973 A1 discloses another rotor of a motor device. OVERVIEW OF THE INVENTION

[0008] Embodiments of the present invention relate to a rotor of a motor device in which a first core part can be prevented from being deformed by a press-fitting force of a shaft and a torque density can be improved.

[0009] In one embodiment, a rotor of a motor device may include: a shaft; a first core part including a first press-fit ring into which the shaft is press-fitted, and a plurality of first cores arranged in the circumferential direction of the first press-fit ring to hold magnets; a second core part including a plurality of second cores arranged in the circumferential direction of the first press-fit ring to face the first cores; and a third core part disposed inside the second cores and installed to hold the first press-fit ring, wherein the second cores have a greater thickness than the first cores.

[0010] The outer peripheral surface of the third core part may be separated from the inner ends of the second cores.

[0011] The third core part may be formed in the shape of a circular ring to hold the entire first press fit ring.

[0012] The inner peripheral surface of the third core part can be pressed against the outer peripheral surface of the shaft.

[0013] Each of the first cores may include: a first connecting rib protruding in a radial direction from the outer peripheral surface of the first press-fit ring; and a first core body connected to the first connecting rib and formed in a fan shape.

[0014] The first connecting rib may form a magnetic leakage flux path through which a magnetic flux generated by the rotor is transmitted toward the shaft.

[0015] The first core body may have a first limiting protrusion formed on its outer side to limit an outer corner of the magnet.

[0016] A first insertion restricting part may be formed at the connection between the first connecting rib and the first core body to restrict an inner corner of the magnet.

[0017] A distance between the first connecting ribs that are adjacent to each other may be smaller than a distance between the first core bodies that are adjacent to each other.

[0018] The second core may be formed in a fan shape and arranged to face the first core, and the second core may have a second guide projection formed on its outer surface, the second guide projection serving to guide the magnet when the magnet is installed.

[0019] The second core may have a second push-preventing protrusion formed at its inner end, the second push-preventing protrusion serving to prevent the inner end of the magnet from being pushed toward the first press-fit ring when the magnet is installed. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing a rotor of a motor device according to an embodiment of the present invention. Fig. 2 is an exploded perspective view showing the rotor of the motor device according to the embodiment of the present invention. Fig. 3 is an exploded perspective view showing the first to third core parts in the rotor of the motor device according to the embodiment of the present invention. Fig. 4A and Fig. 4B are plan views showing the first core part in the rotor of the motor device according to the embodiment of the present invention. Fig. 5A and Fig. 5B are plan views showing the second core part in the rotor of the motor device according to the embodiment of the present invention. Fig. 6 is an exploded perspective view illustrating that the plurality of second core pieces are installed between the respective first core pieces in the rotor of the motor device according to the embodiment of the present invention. Fig. 7 is a table showing a torque per first core part and the maximum load of a press-fitted part depending on the number of first core parts in the rotor of the motor device according to the embodiment of the present invention. Fig. 8 is a graph showing the maximum load of the press-fitted part for each number of first core parts in the rotor of the motor device according to the embodiment of the present invention. DESCRIPTION OF SPECIFIC EMBODIMENTS

[0020] A rotor of a motor device according to an embodiment of the present invention will be described in more detail below with reference to the accompanying drawings. It should be noted that the drawings are not exactly to scale, and the thickness of lines or size of components may be exaggerated solely for ease of description and clarity. Furthermore, the terms used herein are defined to reflect the functions of the invention and may be changed depending on the usage or intention of users or operators. Therefore, the definition of the terms should be determined in accordance with the overall disclosures set forth herein.

[0021] Fig. 1 is a perspective view showing a rotor of a motor device according to an embodiment of the present invention, Fig. Fig. 2 is an exploded perspective view showing the rotor of the motor device according to the embodiment of the present invention, Fig. 3 is an exploded perspective view showing the first to third core parts in the rotor of the motor device according to the embodiment of the present invention, Fig. 4A and Fig. 4B are plan views showing the first core part in the rotor of the motor device according to the embodiment of the present invention, Fig. 5A and Fig. 5B are plan views showing the second core part in the rotor of the motor device according to the embodiment of the present invention, and Fig. 6 is an exploded perspective view illustrating that the plurality of second core pieces are installed between the respective first core pieces in the rotor of the motor device according to the embodiment of the present invention.

[0022] According to Fig. 1 to 6, the rotor of the motor device according to the embodiment of the present invention may include a shaft 10, a first core part 20, a second core part 30, and a third core part 40.

[0023] The shaft 10 can be arranged at the rotation center of the rotor. The shaft 10 can be made of a magnetic material. Since the outer surface of the shaft 10 is subjected to a knurling process, the shaft 10 can have a high surface roughness. This prevents the shaft 10 from slipping on the first core part 20.

[0024] The first core part 20 may include a press-fit ring 21 into which the shaft 10 is press-fitted, and a plurality of first cores 23 arranged in the circumferential direction of the first press-fit ring 21 to hold magnets 50.

[0025] The first press-fit ring 21 may be formed in the shape of a circular ring to be pressed against the outer peripheral surface of the shaft 10. The inner peripheral surface of the first press-fit ring 21 may be pressed against the outer peripheral surface of the shaft 10 and serve to transmit a drive torque of the rotor, which is caused by an electromagnetic force, to the shaft 10.

[0026] The plurality of first cores 23 may be arranged at equal intervals around the circumference of the shaft 10. The first cores 23 may be formed in a fan shape, and the magnets 50 may be arranged between the respective first cores 23. The magnets 50 may be formed in the shape of a rectangular plate.

[0027] The second core part 30 may include a plurality of second cores 31 arranged in the circumferential direction of the shaft 10 and facing the respective first cores 23. The second cores 31 may be divided into a number corresponding to the number of poles in the motor device. The second core 31 may have a greater thickness than the first core 23. The second cores 31 may be arranged at equal intervals on the circumference of the shaft 10 and correspond one-to-one to the first cores 23. The second cores 31 may be fan-shaped, and the magnet 50 may be arranged between the second cores 31.

[0028] The third core part 40 may be installed within the second cores 31 to hold the first press-fit ring 21. The third core part 40 may be formed in the shape of a circular ring to hold the entire first press-fit ring 21. Since the third core part 40 has the same inner diameter as the first press-fit ring 21, the inner diameter of the third core part 40 and the inner diameter of the first press-fit ring 21 can successively form the press-fit surface of the shaft 10. Since the third core part 40 is installed to hold the first press-fit ring 21, the first core part 20 can be prevented from being deformed when the shaft 10 is press-fitted into the first press-fit ring 21.

[0029] The outer peripheral surface of the third core part 40 may be separated from the inner ends of the second cores 31. Since the third core part 40 is separated from the second cores 31, magnetic fluxes generated by the second core part 30 can be prevented from leaking toward the third core part 40. Therefore, it is possible to suppress a reduction in the magnetic flux density of the rotor. Furthermore, since magnetic fluxes hardly leak through the third core part 40, the third core part 40 can have no influence on the overall size of the motor device. That is, the third core part 40 can facilitate the press-fitting of the shaft 10, exerting almost no influence on the magnetic circuit of the motor device.

[0030] Since hardly any leakage fluxes leak through the second and third core parts 30 and 40, it is possible to manufacture a spoke motor using a ferritic permanent magnet and a motor device with a hollow rotor.

[0031] Since the outer peripheral surface of the third core part 40 and the inner ends of the second cores 31 are separated from each other to prevent magnetic flux leakage, the third core part 40 may be made of the same magnetic material as the first and second core parts 20 and 30. Furthermore, the third core part 40 may be made of a non-magnetic material such as synthetic resin, stainless steel, or aluminum.

[0032] The inner peripheral surface of the third core part 40 can be pressed against the outer peripheral surface of the shaft 10. Since the inner peripheral surface of the third core part 40 is pressed against the outer peripheral surface of the shaft 10, the third core part 40 can be prevented from slipping on the outer peripheral surface of the shaft 10 when the rotor is rotated.

[0033] The rotor may have end plates 60 installed at both ends in the axial direction. The end plate 60 may be formed in the shape of a circular ring. The end plate 60 may be made of a non-magnetic material, such as aluminum. The end plate 60 may prevent the first to third core parts 20 to 40 and the magnets 50 from slipping or moving axially on the shaft 10. The end plate 60 may be press-fitted onto the shaft 10.

[0034] The first to third core parts 20 to 40 can be connected to each other by means of an adhesive or an embossed structure. The magnets 50 can also be connected to the first and second core parts 20 and 30 by means of an adhesive.

[0035] The first core 23 may include a first connecting rib 24 and a first core body 25. The first connecting rib 24 may protrude in a radial direction from the outer peripheral surface of the first press-fit ring 21. The first core body 25 may be connected to the first connecting rib 24 and formed in a fan shape.

[0036] The first connecting rib 24 can form a magnetic flux leakage path through which magnetic fluxes generated by the rotor are transmitted toward the shaft 10. The first core part 20 can prevent the second core part 30 and the magnet 50 from slipping or moving in the direction of a centrifugal force when the centrifugal force is generated by the rotor. When the rotor is rotated, the centrifugal forces of the second core part 30 and the magnet 50 can be transmitted to the first core part 20. Therefore, since a stress caused by the centrifugal forces is most concentrated at the first connecting rib 24, the dimension of the first connecting rib 24 can be determined by a kinematic analysis of the concentrated stress.

[0037] The first core body 25 may have a first limiting protrusion 27 formed on its outer surface to limit an outer corner of the magnet 50. The first limiting protrusion 27 may protrude toward the outer corner of the magnet 50. Because the first limiting protrusion 27 limits the outer corner of the magnet 50, the magnet 50 can be prevented from slipping or moving in the direction of the centrifugal force of the rotor.

[0038] At the junction between the first connecting rib 24 and the first core body 25, a first insertion restricting portion 28 may be formed to restrict an inner corner of the magnet 50. At this time, the distance between the adjacent first connecting ribs 24 may be smaller than the distance between the adjacent first core bodies 25. Since the inner corner of the magnet 50 is locked to and restricted by the first insertion restricting portion 28, the insertion depth of the magnet 50 can be restricted such that the magnet 50 is locked to the first insertion restricting portion 28 and prevented from entering the interior when the magnet 50 is inserted between the first cores 23. Therefore, the magnet 50 can be installed at a predetermined radius to the shaft 10.

[0039] The first insertion restriction part 28 may be separated from the shaft 10 by a distance equal to the sum of the width of the first interference fit ring 21 and the length of the first connecting rib 24. Therefore, the inner end of the magnet 50 may be separated from the shaft 10 by the first insertion restriction part 28.

[0040] The second core 31 may be formed in a fan shape to face the first core 23 and have a second guide protrusion 33 formed on its outer side, the second guide protrusion 33 serving to guide the magnet 50 when the magnet 50 is installed. The second guide protrusion 33 may protrude toward an outer corner of the magnet 50. Therefore, when the second core 31 and the magnet 50 are pushed toward the shaft 10 with the magnet 50 disposed between the second cores 31, the outer corner of the magnet 50 may be locked to the second guide protrusion 33 and installed on the second core 31. Furthermore, the second guide protrusion 33 may prevent the magnet 50 from slipping or moving in the direction of centrifugal force when the rotor is rotated.

[0041] The second core 31 may have a second push-preventing protrusion 35 formed at its inner end. The second push-preventing protrusion 35 serves to prevent the inner end of the magnet 50 from being pushed toward the first press-fit ring 21 when the magnet 50 is installed. Therefore, the magnet 50 can be installed at a predetermined radius from the shaft 10.

[0042] The second core parts 30 and the first core parts 20 can be layered alternately (see Fig. 2). In this case, since the number of first core pieces 20 press-fitted onto the shaft 10 is increased, the maximum load on the motor device when the rotor is rotated can be increased.

[0043] Furthermore, the plurality of second core parts 30 may be layered between the respective first core parts 20 (see Fig. 6). Since the thickness of the second core part 30 is relatively increased between the first core parts 20 that are adjacent to each other, the torque of the motor device can be relatively increased when the rotor is rotated. Since the proportion of the second core parts 30 in the entire rotor is increased, the torque density and the magnetic flux density can be relatively increased.

[0044] The number of first core parts 20 layered in the rotor can be determined by the following torque and load analysis.

[0045] Fig. 7 is a table showing a torque per first core part and the maximum load of a press-fitted part depending on the number of first core parts in the rotor of the motor device according to the embodiment of the present invention, and Fig. 8 is a graph showing the maximum load of the press-fitted part for each number of first core parts in the rotor of the motor device according to the embodiment of the present invention.

[0046] According to Fig. 7 and Fig. 8, when the maximum torque of the motor device is 1.7 Nm and the motor device 14 has first core parts 20 installed therein, the torque of each of the first core parts 20 is 0.121 Nm (1.7 / 14) and the maximum load of the first interference fit ring 21 is 5.182 MPa.

[0047] Further, when the maximum torque of the motor device is 1.7 Nm and the motor device 10 has first core parts 20 installed therein, the torque of each of the first core parts 20 is 0.170 Nm (1.7 / 10) and the maximum load of the first interference fit ring 21 is 7.271 MPa.

[0048] Further, when the maximum torque of the motor device is 1.7 Nm and the motor device has 6 first core parts 20 installed therein, the torque of each of the first core parts 20 is 0.283 Nm (1.7 / 6) and the maximum load of the first interference fit ring 21 is 12.07 MPa.

[0049] Since the torque and the maximum load increase as the number of installation of first core parts 20 increases, the number of installation of first core parts 20 can be appropriately designed taking into account the size or characteristic of the motor device.

[0050] According to the embodiment of the present invention, since the third core part is installed to hold the first press-fit ring, the first core part can be prevented from being deformed when the shaft is press-fitted into the first press-fit ring.

[0051] Furthermore, since the third core portion is separated from the second cores, magnetic fluxes generated by the second core portion can be prevented from leaking toward the third core portion. Therefore, it is possible to prevent a reduction in the magnetic flux density of the rotor.

[0052] Although preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will recognize that various modifications, additions, and substitutions are possible without departing from the scope and spirit of the invention disclosed in the appended claims.

Claims

[1] Rotor of a motor device comprising: a shaft (10); a first core part (20) comprising a first press-fit ring (21) into which the shaft (10) is press-fitted, and a plurality of first cores (23) arranged in the circumferential direction of the first press-fit ring (21) so as to hold magnets (50); a second core part (30) having a plurality of second cores (31) arranged in the circumferential direction of the first press-fit ring (21) so as to face the first cores (23); and a third core part (40) arranged within the second cores (31) and installed to hold the first press-fit ring (21), wherein the second cores (31) have a greater thickness than the first cores (23). [2] A rotor of a motor device according to claim 1, wherein the outer peripheral surface of the third core part (40) is separated from the inner ends of the second cores (31). [3] A rotor of a motor device according to claim 2, wherein the third core part (40) is formed in the shape of a circular ring to hold the entire first press-fit ring (21). [4] A rotor of a motor device according to claim 3, wherein the inner peripheral surface of the third core part (40) is pressed against the outer peripheral surface of the shaft (10). [5] A rotor of a motor device according to claim 1, wherein each of the first cores (23) comprises: a first connecting rib (24) projecting in a radial direction from the outer peripheral surface of the first press-fit ring (21); and a first core body (25) connected to the first connecting rib (24) and formed in a fan shape. [6] A rotor of a motor device according to claim 5, wherein the first connecting rib (24) forms a magnetic leakage flux path through which a magnetic flux generated by the rotor is transmitted toward the shaft (10). [7] A rotor of a motor device according to claim 5, wherein the first core body (25) has a first limiting projection (27) formed on its outer side to limit an outer corner of the magnet (50). [8] A rotor of a motor device according to claim 5, wherein a first insertion restricting part (28) is formed at the junction between the first connecting rib (24) and the first core body (25) to restrict an inner corner of the magnet (50). [9] A rotor of a motor device according to claim 8, wherein a distance between the first connecting ribs (24) adjacent to each other is smaller than a distance between the first core bodies (25) adjacent to each other. [10] A rotor of a motor device according to claim 5, wherein the second core (31) is formed in a fan shape and is arranged to face the first core (23), and the second core (31) has a second guide projection (33) formed on its outer side, the second guide projection (33) serving to guide the magnet (50) when the magnet (50) is installed. [11] A rotor of a motor device according to claim 10, wherein the second core (31) has a second push-preventing projection (35) formed at its inner end, the second push-preventing projection (35) serving to prevent the inner end of the magnet (50) from being pushed toward the first press-fit ring (21) when the magnet (50) is installed.

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